The present invention relates to a drilling unit for printed circuit boards having two operating heads.
The machining of printed circuit boards increasingly necessitates operating machines with high levels of versatility and productivity. For this purpose drilling machines have been proposed which are provided with a series of operating heads adapted to drill simultaneously a corresponding series of like boards. These machines, although having high productivity, are generally not very versatile, particularly in the case of boards of greater width than the distance provided between the operating heads.
Modular drilling units have also been proposed, which can optionally be connected to a single control unit with a view to adapting the size of each installation to the respective production requirements. However, each drilling unit operates like a drilling machine with a single operating head, in which case the relative productivity is comparatively low.
A drilling machine is also known having a table which can move along the usual Y-axis, on which can be arranged a series of boards, also of different dimensions. The drilling machine has a series of operating heads which can move along the usual X-axis independently of one another. In this way the heads can operate on boards of different dimensions and/or different distribution of the holes.
In particular, each head is provided with laterally projecting arms, which carry the support slides on the cross-piece for guiding the heads, and they are offset with respect to those of the adjacent head. Moreover, the guide cross-piece is provided with a fixed screw common to all the heads, whereas each head is provided with an electric motor which actuates a corresponding nut. In this way two or more heads can be used to carry out drilling on the same board, thereby increasing the productivity of the drilling machine.
This drilling machine has a number of disadvantages. Firstly, the construction of each head integrated with the displacing motor along the X-axis and with a nut is expensive and not very reliable in operation. Moreover, the arms carrying the support slides and the common screw extending over the entire length of the cross-piece are subject to elastic and thermal deformation, thereby giving rise to inaccuracy in machining. In turn, the cross-piece has to extend beyond the machining zone so as to provide a parking area for the heads which are sometimes inoperative.